Wikipedia:Reference desk/Archives/Science/2012 October 17

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October 17

Chemistry to dissolve human poo?

What does human poo consist of? fats? protein? is it polar or non polar? and more importantly what is the chemistry that will dissolve it? just like alcohol dissolve oil etc. Electron9 (talk) 02:24, 17 October 2012 (UTC)

What is the chemistry? Don't you mean solvent? It's a complex mixture of both polar and non-polar compounds. Plasmic Physics(talk) 02:28, 17 October 2012 (UTC)

This topic is extensively covered in our article on wastewater treatment. Nimur (talk) 02:31, 17 October 2012 (UTC)

Seems to normally be low on fats, so will just dissolve in water with a bit of agitation. However, some people with non-functional gall bladders or using diet products like Orlistat do pass substantial portions of fat, so adding some detergent would cover those cases. StuRat(talk) 02:38, 17 October 2012 (UTC)

A significant amount of poo is cellulose, which isn't soluble in either detergent or water. --Jayron32 02:50, 17 October 2012 (UTC)

Ah yes, and there's always the corn kernels to deal with, along with seeds and perhaps grains of sand, which aren't going to dissolve in anything short of a powerful acid or base. StuRat (talk) 06:30, 17 October 2012 (UTC)

What's the best household- or easily obtainable chemical to dissolve cellulose ..? Electron9 (talk) 03:15, 19 October 2012 (UTC)

Does bleach work ? StuRat (talk) 22:05, 19 October 2012 (UTC)

Bleach is mostly water, so no, it would not dissolve cellulose. Oxidise does not equal dissolve. Plasmic Physics (talk) 02:39, 20 October 2012 (UTC)

It really depends on what the underlying aim is. Biological washing powders are designed to deal with organic dirt by the use of enzymes. In the laboratory solubalizers such as Soluene might be more appropriate. For drains a mechanical resolution is often resorted to. Rich Farmbrough, 17:48, 27 October 2012 (UTC).

Mystery leaf 'streamers'

Maple leaf with 'streamers'

I took the photograph at right this weekend in central Ontario, Canada, about 100 km north of Toronto. It was on a small maple tree, on which a number of leaves had these dark, vertical 'streamers' (about 1 cm long) sticking out of their upper surfaces. Some leaves had just a few, others (like the one pictured) were heavily covered.

Can anyone tell me what these streamers are? KevinHadley (talk) 03:44, 17 October 2012 (UTC)

Maple spindle galls, caused by a mite. http://www.uoguelph.ca/pdc/Factsheets/Diseases/Maple_Galls.htm μηδείς (talk) 04:01, 17 October 2012 (UTC)

That's pretty neat, the mites are able to alter the leaf cells to grow a gall around them. Tiny genetic engineers at work. StuRat (talk) 06:27, 17 October 2012 (UTC)

Not genetic - it's mostly the result of hormonal effects. Roger (talk) 11:11, 17 October 2012 (UTC)

Neat. Thanks! KevinHadley (talk) 13:49, 17 October 2012 (UTC)

• Wikipedia does have a short article on Galls, which may lead the reader to other information as well. --Jayron32 13:53, 17 October 2012 (UTC)

Why Lube oil consumption of Gas Engine increase after major overhauling.

"Why Lube oil consumption of Gas Engine increase after major overhauling — Precedingunsigned comment added by 182.182.122.148 (talk) 06:20, 17 October 2012 (UTC)

Is that a gasoline engine ? And did they mill down the cylinders ? StuRat (talk) 06:26, 17 October 2012 (UTC)

Gas engine or gasoline engine, taking it that it is in any case a spark ignition piston engine: In vintage engines, a temporary increase in oil consumption above normal tended to occur as carbon at the top of the piston formed a seal - the carbon got removed in overhaul and needs to build up again. However in modern engines, especially for bowl-in-piston/squish land piston/EE-type combustion chambers, a noticeable increase (as distinct from a modest increase) in oil consumption is a sign of errors in rebuilding. Posible errors are: cylinders not correctly honed, incorrect oversize piston and/or rings fitted wrt cylinder re-bore, piston rings incorrect or incorectly fitted, problems with valve guides. A possible problem is the oil presure control spring together with tight bearings causing higher oil pressure leading to over lubrication of valve gear. At one time, new engines and overhauled engines were initially filled with "running-in" low-viscosity oil, which also increases consumption, but this should not be done nowadays. Wickwack124.178.143.72 (talk) 08:17, 17 October 2012 (UTC)

also, minor oil consumption can be caused by lack of absolute cleaning before final assembly which can lead to scoring of cylinder walls, particles lodging in ring grooves, etc. It's also possible that initial ring sealing after rebuild will be not quite as perfect as modern factory engine construction, and will improve somewhat after a little break in period, like in the old days. Gzuckier (talk) 04:27, 27 October 2012 (UTC)

New exoplanet temperature

See [1]. That says the surface temperature is around 2200°F, due to it's proximity to the star. However, at that distance it's sure to be tidally locked to it's star (unless the planet is very young). If we also assume it to have no atmosphere or liquid covering it (having been blown off by the solar wind), wouldn't the dark side be far cooler ? StuRat (talk) 09:03, 17 October 2012 (UTC)

I don't see why not, without a thermal vector, there is no way for heat to be distributed except by good old fashioned conduction. I assume that you're aware of Mercury (planet). Plasmic Physics (talk) 10:35, 17 October 2012 (UTC)

StuRat, you beat me to it! I even wonder if outgassing from the magma side would lead to frozen atmosphere accumulating on the dark side, with the occasional cryovolcano of liquid water and room temperature air awaiting such Robinson Crusoes as our imaginations can devise. :) Wnt (talk) 16:54, 17 October 2012 (UTC)

(ec) This article about the newly discovered planet says near the bottom:

And whichever side of the planet faced the star would be broiling hot, with the other side icy cold.

This doesn't actually say that it's tidally locked, but it makes your point about the surface temperature not being high everywhere.Duoduoduo (talk) 17:00, 17 October 2012 (UTC)

Why do you mention Mercury in this context? Do you perhaps hold the common incorrect pre-1965 assumption that Mercury is tidally locked to the Sun, making its supposed dark side cold? Are you aware of Mercury (planet)? 88.112.36.91 (talk) 20:41, 17 October 2012 (UTC)

I was refering to the effect of a combination of a slow sidereal period, and a lack of atmosphere, to produce a large temperate gradient. Plasmic Physics (talk) 22:02, 17 October 2012 (UTC)

The article says that the dark side of Mercury averages just 110 K, with a "reaches 100 K at night" figure. I don't know if it would reach 77 K and allow nitrogen to condense out if it were locked 1:1 with its orbit. (or 90K for liquid oxygen, if it somehow came to exist; come to think of it, liquid methane at 110 K would be plausible, maybe, if it weren't constantly re-boiled and lost?) Clearly for any satisfying scenario with a reservoir of frozen/boilable atmosphere on Bb, a complete tidal lock would be preferred. But at 0.04 AU ... shouldn't it be? Wnt (talk) 22:13, 17 October 2012 (UTC)

I should correct myself: not slow sidereal period, but a ratio close to one, between sidereal rotational period and orbital period. A ration of 1:1 would indicate tidally locked. A ration of 1:1.5 for mercury is enough to produce a gradient. Plasmic Physics (talk) 01:31, 18 October 2012 (UTC)

To clarify, any low ratio would work to have a cold nightside. But very precisely 1:1 is needed in order for a base on the nightside to last for long. :) I don't understand exactly what happens to atmosphere on this sort of planet, but we know from Venus that even a very slow rotation is enough to keep the whole planet unbearably hot. I don't know if there's a scenario for Bb development that would allow all that atmosphere to condense out on a stationary dark side. Wnt (talk) 17:22, 22 October 2012 (UTC)

Who mentioned a base on the nightside? (Not that I disagree) Of course, Venus' even temperature is due to its atmosphere, precluding it according to my second post. Plasmic Physics (talk) 10:09, 26 October 2012 (UTC)

Appearance

• As an aside, I should mention that the artist's rendition from the article and as shown on our Main Page seems wrong to me. If it's hot enough to melt magma, shouldn't at least some of the planet's edge be visibly red? (see Incandescence, which starts at 525 C) Also, the graphic gives me the impression that from close by the planet, its star looks little bigger than the Moon; but it's only 20 times the distance from the Moon to Earth away from the planet, and nearly as big and half as bright as the Sun. Erm, to put that more simply, at 0.04 AU its star should look 25 times wider than the Sun, and I'm just not feeling that from the picture. Wnt (talk) 22:20, 17 October 2012 (UTC)

The surface may not glow bright enough to be visible with the star in the field of view. Also, if it is tidally locked with no atmosphere, then only the part illuminated by the star would be hot (that was the point of Stu's question), and that glow would be drowned out by the starlight. As for the sizes, that's going to depend on how far away the "camera" is from the planet and the star. The star has about half the apparent diameter of the planet. Since the star is actually about 100 times bigger (assuming the planet is about the size of Earth), that suggests the distance from the the camera to the Sun is about 200 times the distance from the camera to the planet. That puts it about 30,000 km away from the planet.

When viewed from the Earth, the Moon and Sun are both about 0.5 degrees in diameter. Alpha Centauri B from 0.04 AU would 11 degrees (just under 25 times wider). There is no way to know what the angular diameter is from an image like that, though - you would need to know what the total field of view was.--Tango (talk) 18:55, 18 October 2012 (UTC)

perverted justice

I've taken the liberty of moving this question to Wikipedia:Reference desk/Humanities#Perverted Justice (moved from Science Refdesk). Trust me, this is a good thing - you'll get better answers. Wnt (talk) 16:49, 17 October 2012 (UTC)

does a nurse need to expel air from a prefilled flu vaccine

when administering a prefilled flu vaccine does the nurse need to expel any air from the syringe —Preceding unsigned comment added by 95.146.101.33 (talk) 10:54, 17 October 2012 (UTC) |}

Two answers: [1] in general, no, because prefilled syringes generally don't contain air. [2] But if a nurse noted air, in general, he would expel it out of an abundance of caution rather than because it presented any real danger. As a rough estimate, it would take at least 20 cc of air injected directly into the bloodstream to cause an air embolism. A flu vaccination is about 0.5 cc: even if the whole syringe were air, it wouldn't be fatal. And it's also not going into the bloodstream, but intradermally or intramuscularly. See The Straight Dope for more discussion of how much air can be fatal. - Nunh-huh 16:19, 17 October 2012 (UTC)

Air injected into a muscle or under the skin is not particularly dangerous -- it might hurt like hell, though. Looie496 (talk) 16:27, 17 October 2012 (UTC)

If you Google this question, you actually can find multiple bulletin boards of nurses discussing a wide variety of practices. It seems that some vaccines recommend you do, and some recommend that you don't, and most don't say anything at all. I'm not sure there's any real consensus on it. But this is just a Google survey; I have no direct knowledge of this topic. --Mr.98 (talk) 22:44, 17 October 2012 (UTC)

I was recently self-injecting Clexane subcutaneously daily for a few weeks, every prefilled syringe had a small amount of air in it, and the instructions specifically stated "Do Not Remove the air before injection". I asked a few nurses and doctors about it, and their conclusion was that "amateurs" would probably expel half the drug trying to get the air out, and that small amount of air sub-cutaneously would do no harm at all.124.191.177.92 (talk) 07:42, 18 October 2012 (UTC)

Depending on the design of the syringe, there is often a dead volume (why is that red?) that is not expelled when the plunger is pushed all the way in. If the syringe is prefilled "to contain" the stated volume of liquid, the dead volume represents an amount of the stated volume that does not get delivered. If there is a small amount of air also, one can push out all the liquid because the air can be what remains in the dead volume. Calibrating "to deliver", one would include extra volume of liquid to compensate for what gets retained in the dead volume. I have no idea if this is how/why medical folks do what they do, but it's what I've seen done in other syringe-transfer work. DMacks (talk) 02:22, 19 October 2012 (UTC)

Human "fuel efficiency"

We tend to think of biking and walking as "green" alternatives to driving, but it seems to be this may not be true in some cases. Walking and biking don't use fossil fuels, but inasmuch as they require greater physical exertion, they could lead to more eating—human fuel, if you will. Since the production, transportation, and preparation of that food is almost never carbon neutral, could a person be making a more environmentally responsible decision by driving in some cases? If we were to graph it, I could see car efficiency increasing on longer trips. And perhaps hybrid or electrical cars could shift the graph a bit. --BDD (talk) 20:58, 17 October 2012 (UTC)

Keep in mind that fossil fuels are non-renewable (at least not for millions of years) and also release net carbon dioxide which was previously safely sequestered underground. Also, you assume that biking and walking cause you to eat more. Hopefully you lose some excess weight, instead. Then there's the improvement on your health and the inefficiency in caring for unhealthy people (with diabetes and such) to consider. There's also the concept that using a car more wears it out, while using the body more (within limits) actually makes it last longer. But, I suppose, if you have a future solar/battery powered car which is fully charged (so wasting any additional sunlight), then using it might not be bad alternative. StuRat (talk) 21:05, 17 October 2012 (UTC)

If you do the measurement of human efficiency, you have to keep in mind that when you walk/bike to work, you are moving a far smaller mass than if you were driving a car. It's about energy per person-mile. I believe my car weighs over ten times what I do, so I only have to be 10% as efficient as the car to break even. Someguy1221 (talk) 22:25, 17 October 2012 (UTC)

BDD is on the ball and has asked a very good question. In Mark's Standard Handbook for Mechanical Engineers, 11th ED, EA Avallone et al eds, 2007 McGraw-Hill, it says on page 9-5 that the [maximum useable, continous over a work day] power output of a typical healthy adult human is about 400 W, and when compared to the amount of food required to sustain this, the thermodynamic efficiency is about 25% - about the same as a typical 4-stroke gasoline engine under optimal speed and load conditions, but nowhere near as good as a modern turbocharged diesel engine (~40 to 45%). It also says that the maximum human mechanical power output (typical fit adult male) is about 1500 W sustainable for only 0.6 seconds. It should be noted that under typical driving conditions, a car gasoline engine is not operating at optimal load, so the real efficincy will be less than 25%. Incidentally, when I was about 16, I took up intensive weight training at the local YMCA. My appetite increased dramatically, and I've had trouble controlling my weight ever since. The fuel efficiency of fit humans is surpisingly good - old books give data for utilizing animals such as horses to power mills, water pumps, etc, the calorific value of the feed required makes them woeful compared to the IC engine, probably because typical work animals (horses, oxen) all eat food full of cellulose, which has calorific value but is difficult to digest. Ratbone 124.178.52.68 (talk) 00:11, 18 October 2012 (UTC)

However, supposing that vigorous cycling makes you eat an extra loaf of bread a day, that apparently equals around one kilogram of extra carbon dioxide.[2]. According to this table you get 328 grammes of CO2 when you drive one mile in a petrol (gasolene) car or 327 in a diesel one. So you get about 3 miles in your car instead of a loaf of bread. (PS I'm not a scientist, so there may be a serious flaw in my thesis).Alansplodge (talk) 18:20, 18 October 2012 (UTC)

But the carbon in that loaf of bread came from the atmosphere through photosynthesis, so you breathing it back into the atmosphere just gets you back where you started - it's just the carbon cycle. The problem with fossil fuels is that the carbon was sequestered underground for millions of years and would have stayed there had we not burned it. That introduces more carbon into the carbon cycle, which is the problem. --Tango (talk) 19:05, 18 October 2012 (UTC)

You're using the wrong metric, though - we're interested in energy per mile, not energy efficiency. The amount of energy required to travel a mile is going to be very different for a car than a person walking. A car travelling at 60mph has to use a lot more energy to overcome air resistance than a person walking at 3mph. As SomeGuy mentioned, a car is a lot heavier than a person. I don't know the numbers, but I expect cars use far more energy than people to travel the same distance, so even if the car was 100% efficient it would still need more fuel. --Tango (talk) 19:05, 18 October 2012 (UTC)

How much fossil CO2 was released in the course of converting 8g of wheat seed in a farm supply store into a loaf of bread in the OP's kitchen 500km from the farm. That's the real question that needs to be answered. Roger (talk) 19:52, 18 October 2012 (UTC)

To answer your's and Tango's points, the first site that I linked to is talking about carbon footprint rather than carbon capture. An 800g loaf couldn't possibly store 1000g of CO2. So the 1kg of CO2 that I quoted includes all the fossil fuel used in the production, processing and retailing of the loaf. Alansplodge (talk) 21:24, 18 October 2012 (UTC)

The bread can supply the carbon, which your body then combines with oxygen from the air, to produce carbon dioxide, which is exhaled. So, it is possible for the mass of CO₂ produced using a loaf of bread to be higher than the mass of the bread itself. Also note that if you consider all the carbon costs of producing that loaf of bread, then you also need to consider all the carbon costs of extracting the raw materials, building and delivering the car, and extracting, refining and delivering the fuel. Those are not insignificant. StuRat (talk) 20:08, 19 October 2012 (UTC)

I think in the spirit of the OP's question it would be best to consider that the car is one of those biodiesel-fueled vehicles that runs on used cooking oil. Renewable fuels are great, but there are still limits on how much carbon we can pull out of the atmosphere with the available arable land.Wnt (talk) 20:13, 18 October 2012 (UTC)

Also, exercise is necessary for most people to be optimally-healthy and if they're going to go exercise at the gym, or running around their city or the countryside or swimming at the pool, they might as well using that effort to transport themselves for utilitarian purposes. 2.97.23.83 (talk) 17:46, 26 October 2012 (UTC)

The "whole question" of carbon footprint of human energy gets enormous. Compare the total carbon footprint of 500 calories of apples produced by a tree in you backyard that you don't bother fertilizing, versus that of 500 calories of beef grown in former Amazon rainforest by slash and burn agriculture. (Just for extremes; for fun, consider 500 calories of beef grown in your backyard by cattle eating naturally growing grass that you don't fertilize, versus apples grown with use of (synthetic) ammonium nitrate and flown in to the US from New Zealand or somewhere. But I think the first guy is right, the major factor of car vs bike is whether you have to haul the extra 2 tons of metal around with you or not. Gzuckier (talk) 04:35, 27 October 2012 (UTC)

Also if I drive 5 miles to buy food to enable me to walk 2 miles it's a loss for everything except my health (possibly). Rich Farmbrough, 18:04, 27 October 2012 (UTC).